Kenaf (hibiscus cannabininus) is an annual fibrous, non-wood plant, lignocellulosic material, originally native to the East Indies, but now widely cultivated. The plant grows quickly to a height of as much as 5.5 m (18 ft.). The plant is comprised of two distinct fiber types--outer bast fibers and an inner core material. The core comprises 60-75 percent of the plant by weight.
The bast fiber has historically found application as cordage, and in the manufacture of canvas. It is now being considered for use as a source for paper manufacture. To use the bast fiber, it must be separated from the core. This is conventionally done through the use of conventional forage harvesters which chop bulk kenaf into lengths of 3-5 inches which comprise both bast and core. The bast and core are typically packaged using conventional module builders, the modules then being fed into a processing plant, which breaks the module open, passing into a conventional separation cylinder--a large rotating drum with a series of screens and baffles. As the bast is the lighter of the two fractions, it remains within the separation cylinder. The core material falls through openings in the screens onto a conveyer for recovery and use.
A modification of this process is described in U.S. application Ser. No. 08/393,824, copending herewith, by inventors Fuller, Pote and Chen. Additionally, a newly developed process, using kenaf stalks of substantial length, is disclosed in copending U.S. application Ser. No. 08/261,978. Both applications are incorporated herein by reference. The method of separating the bast from the core does not constitute an aspect of the invention of this application, per se.
Press board, strand board, and other materials made out of wood processing residues, or particulate wood materials, constitute a large industry in the United States which competes with the paper industry for pulp wood materials and the like. Additionally, the raw wood materials employed in this industry are replaced only slowly, and are subject to competitive pressure from a variety of commercial markets. Low, medium and high-density materials are commonly employed as acoustical insulation, thermal insulation, decorative panels, structural panels and the like. These materials are conventionally prepared using lignocellulosic particulate materials such as wood, a binder such as novalak or resole resin, and one or more additives, such as a wax, colorant, etc. The board is often prepared by loading the materials into heated presses, and hot pressing the materials under pressure at a temperature sufficient to cure the synthetic or natural based binder or loaded in a form for a sufficient time to cure (with or without heat) cold-set binders. Physical dynamics, as well as water absorbency characteristics are important properties considered.
Accordingly, it remains an object of the industry to provide lignocellulosic, non-wood material for low-density press board and the like. Additionally, it remains an object of the industry to find a suitable commercial use for kenaf core separated from the bast outer fiber.